Iron protein microbial

Nitrile hydratase is a key enzyme involved in the microbial degradation of nitriles in the environment, catalyzing the hydration of a nitrile to an amide (see Iron Proteins with... 

Ferredoxins. Name for a group of non-hem iron proteins of animal, plant, or microbial origin that usually contain equal numbers of iron and labile sulfide ions 2,4,6, or 8 of each. The 2-iron-F. [96-98 amino acid residues, 4-6 of which are cysteine (Cys)] contain the four-membered rings shown in the Figure these are bound by two cysteine residues per iron atom to the protein. The 4-iron-F. and the 8-iron-F. (55 amino acid residues) possess one or two cubic clusters (see figure). 

Proton-coupled electron transfer (PCET) is known to play an important role in a variety of biological processes, including microbial iron transport by ferric enterobactin, enzyme catalysis in systems such as fumarate reductase and nitrate reducatase, and dioxygen binding by the non-heme iron protein hemerythrin. " As such, pH-dependent electrochemical studies can play an important role in unraveling these mechanisms. The most heavily studied biological system known to involve PCET is cytochrome c oxidase, the terminal electron-transfer complex of the mitochondrial respiratory chain, which catalyzes the reduction of molecular oxygen to water. ... 

The most intensively studied microbial epoxidizing agent is the co-hydroxylase system of Pseudomonas oleovorans [1156,1157]. It consists of three protein components rubredoxin, NADH-dependent rubredoxin reductase and an co-hydroxylase (a sensitive nonheme iron protein). It catalyzes not only the hydroxylation of aliphatic C-H bonds, but also the epoxidation of alkenes [1158, 1159]. The following rules can be formulated for epoxidations using Pseudomonas oleovorans (Scheme 2.155). 

Finally, animal, plant and microbial tissues have been shown to contain the iron storage protein ferritin. The animal protein has been extensively studied, but the mechanism of iron binding has not been completely resolved (29). Animal tissues contain, in addition, a type of granule comprised of iron hydroxide, polysaccharide and protein. The latter, called hemosiderin, may represent a depository of excess iron (30). Interestingly, a protein with properties parallel to those of ferritin has been found in a mold. Here the function of the molecule can be examined with the powerful tools of biochemical genetics (31). 

One last class of mononuclear non-haem iron enzyme that we have not yet considered, consists of the microbial superoxide dismutases with Fe(III) at their active site. The crystal structure of the E. coli enzyme shows a coordination geometry reminiscent of protocatechuate 3,4-dioxygenase, with four endogenous protein ligands, three His and one Asp residue, and one bound water molecule (Carlioz et ah, 1988). 

Iron homeostasis in mammalian cells is regulated by balancing iron uptake with intracellular storage and utilization. As we will see, this is largely achieved at the level of protein synthesis (translation of mRNA into protein) rather than at the level of transcription (mRNA synthesis), as was the case in microorganisms. This is certainly not unrelated to the fact that not only do microbial cells have a much shorter division time than mammalian cells, but that one consequence of this is that the half-life of microbial mRNAs is very much shorter (typically minutes rather than the hours or often days that we find with mammals). This makes it much easier to control levels of protein expression by changing the rate of specific mRNA synthesis by the use of inducers and repressors. So how do mammalian cells... 

Although mammalian CYPs are attractive candidates for use as commercial biocatalysts, many functional characteristics limit the opportunities to exploit such a system. Association of the enzymes with membranes prevents easy extraction and purification and limits the opportunities to produce useful recombinant enzymes by cloning the relevant genes for expression in microbial systems. All P450s have a porphyrin-haem active site that requires a second protein to reduce the iron component, often cytochrome P450 reductase or... 

Within organisms, organic sulfur is present predominantly as the amino acids cysteine and methionine, and the algal and bacterial osmolyte, dimethylsulfoniopropionate (DMSP). The latter also serves as an antioxidant and cryoprotectant. Small amounts of organosulfur are also present in some polysaccharides, lipids, vitamins, enzymes, and in the iron-sulfur protein ferrodoxin. Cell lysis and microbial degradation releases... 

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